Managing soil structure

in established vineyards

The influence of pores, plants and people on soil

structure in established vineyards

A report for

By Andrew Clarke

2015 Nuffield Scholar

June 2018

Nuffield Australia Project No 1513

Supported by

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Scholar Contact Details

Andy Clarke

Yering Station

38 Melba Hwy

Yering

VIC 3770

Phone: 0417371139

Email: aclarke@yering.com

In submitting this report, the Scholar has agreed to Nuffield Australia publishing this material in its edited form.

NUFFIELD AUSTRALIA Contact Details

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Telephone: (02) 9463 9229.

Mobile:0431 438 684

Email: enquiries@nuffield.com.au

Address: PO Box 1021, North Sydney, NSW 2059

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Executive Summary

The Australian wine industry provides the fifth largest export by value and is produced in a

wide variety of regions, climates and geological areas. The soils these vines grow in are old

and fragile in nature and are readily degraded when managed utilising traditional European

practices. The best time to conduct remedial work on vineyard soil is prior to trellis installation

and planting, as the permanent structures and narrow row spacing commonly used prevent

the use of large scale earthmoving equipment for deep ripping. Novel and long-term

approaches are required to create sustainable systems.

These technical approaches include:

• Minimal topsoil disturbance through tillage.

• Remediation and maintenance of soil chemistry and cation balance.

• Diverse perennial vineyard floor vegetation.

• Utilisation of mulch and compost under the vines.

More sociological approaches are also needed to gain uptake of management change, which

include:

• Dissemination of practical learning through discussion groups and mentor

programs.

• Creating champions for change, sharing best practice and the risks involved

with change.

The current fiscal conditions of the wine industry do not promote large amounts of investment

back into the vineyard. Many gains can however be made through better management

decisions with minimal investment. The gains are small and incremental, and difficult to see

from season to season.

It is critical that farmers continue to try new techniques to continually improve and

understand that not everything trialled will be successful. There is no reason why growers as

custodians of the land should not be sharing success and being brave enough to share failings

to drive the industry towards a sustainable land use approach. Best practice guidelines are

more effectively learnt in practice in the field rather than in the text book, so demonstrations,

field walks, and discussion groups or mentor programs are a great way of sharing this

knowledge. This is not just applicable to soil management practices but all aspects of the

industry, from production, to processing to marketing.

Vineyards take time to develop and mature before the best quality grapes can be produced,

so long-term thinking needs to be employed to maintain the assets. The goal should be to

have healthy, environmentally and financially sustainable vineyards for generations to come.

As an industry, it is vital that growers are as open about failings as successes, in order to

achieve this.

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Table of Contents

Executive Summary ........................................................................................................... 3

Table of Contents .............................................................................................................. 4

Table of Figures ................................................................................................................. 5

Foreword .......................................................................................................................... 6

Acknowledgments ............................................................................................................ 7

Abbreviations ................................................................................................................... 7

Objectives ......................................................................................................................... 8

Chapter 1: Australian vines and soils ................................................................................. 9

What is the Problem? ........................................................................................................... 10

The 3 P’s of Soil Management ......................................................................................... 10

Chapter 2: Pores ............................................................................................................. 12

Soil physical components ..................................................................................................... 12

Cation Exchange capacity ..................................................................................................... 13

Sodic Soils ............................................................................................................................. 14

Amelioration treatments ...................................................................................................... 15

Salinity ................................................................................................................................... 16

Physical treatments .............................................................................................................. 18

Acidification .......................................................................................................................... 19

Chemical ameliorants ........................................................................................................... 20

Cultivation ............................................................................................................................. 21

Compaction ........................................................................................................................... 23

Deep Ripping ......................................................................................................................... 25

Controlled Traffic .................................................................................................................. 25

Chapter 3: Plants ............................................................................................................. 27

The soil food web .................................................................................................................. 27

Microbiological activity ......................................................................................................... 28

Earthworms and arthropods ................................................................................................ 29

Root structures ..................................................................................................................... 29

Midrow Management ........................................................................................................... 29

Undervine management ....................................................................................................... 32

Mulch and Compost .............................................................................................................. 32

Vine Roots ............................................................................................................................. 34

Chapter 4: People ........................................................................................................... 36

Change limiting factors ......................................................................................................... 36

Lack of champions ................................................................................................................ 37

Conclusion ...................................................................................................................... 41

Recommendations .......................................................................................................... 42

References ...................................................................................................................... 43

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Plain English Compendium Summary ............................................................................... 44

Table of Figures

Figure 1: The 3 P's of soil structure .......................................................................................... 10

Figure 2: Distribution of solids, water and air within a typical soil .......................................... 12

Figure 3: Heavily tilled soils of Corton Charlemagne in Burgundy France (Source: Author) ... 13

Figure 4: Sandy Duplex soil CEC readings. (Source: soilquality.org.au) .................................. 14

Figure 5. A duplex clay soil in the Yarra Valley. Note the white bleached layer. (Source: Mark

Krstic) ........................................................................................................................................ 15

Figure 6: The picturesque town of Tubingen Germany is also home to CHT, trialling

organosilicate soil amendment technology ............................................................................. 16

Figure 7: Checking perched water table levels in Almonds in Helm, California (Source:

Author) ..................................................................................................................................... 17

Figure 8: Mounding of a vineyard in the Yarra Valley. The permanent sward hides the slightly

sloping channel through the middle of the block. (Source: Author) ....................................... 18

Figure 9: Soil pH in Australia (Department of Environment, 2010) ......................................... 19

Figure 10: Spreading gypsum and lime in the Yarra Valley in Autumn (Source: Author) ....... 21

Figure 11. Professor Pilar Baeza of Madrid Polytechnic in heavily cultivated Grenache

vineyards of La Mancha Spain (Source: Author) ...................................................................... 22

Figure 12: A heavily cultivated midrow and undervine area in Rutherford, Napa Valley,

California (Source: Author) ....................................................................................................... 23

Figure 13: Tractor tyre marks in a cultivated vineyard in Champagne, France (Source:

Author) ..................................................................................................................................... 24

Figure 14: Specialised over-the-vine tractors and multiple row sprayers are vital in close-

planted vineyards in Burgundy, France (Source: Author) ........................................................ 26

Figure 15: The soil food web (USDA, n.d.)................................................................................ 27

Figure 16: Rick Haney, USDA in Temple Texas with his equipment for measuring soil

respiration (Source: Author) .................................................................................................... 28

Figure 17: Bob Schindelbeck of Cornell University with Bruce Murray of Boundary Breaks

Wines, Finger Lakes District NY (Source: Author) .................................................................... 30

Figure 18: The effects of soil strength on tillage radish grown in the Yarra Valley, Australia

(Source: Author) ....................................................................................................................... 31

Figure 19: Natural Selection Farms composting facility in Washington State (Source: Author)

.................................................................................................................................................. 34

Figure 20: Measuring Soil pH in no till soil in the Pallouse, Washington State (Source: Author)

.................................................................................................................................................. 39

Figure 21: Frederic Thomas at a grower field day in Effiat, France 2015 (Source: Author) ..... 40

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Foreword

Soil structure and its resilience is key to the production of the best grapes for wine production.

It is the role of the viticulturist to deliver the grapes to the winery in the optimal condition for

any given season. Seasonal climatic extremes such as prolonged rainfall in 2011, sustained

heat in 2009 or the drought of the mid to late 2000’s all play their part in shaping the final

wine in the bottle. It is the minimisation of abiotic stress which allows for the best product,

and resilient soils help with this.

Initially, my study topic was centred around the remedial work on subsoil in established

vineyards with the goal of expanding the soil volume available to the vine to reduce stress.

Realising that this is possibly even less considered outside of Australia, I decided to focus on

the most efficient use of the existing topsoil.

During my travels to France, Spain, Germany, Canada, Ireland and the USA it dawned on me

that the greatest limiting factor in the management of soils is often the custodians themselves

and the paradigm through which they make their decisions. Meeting soil scientists Bob

Schindelbeck and Rick Haney in the USA, I began to realise that soil science is as much

sociological as it is about the dirt.

This is what created the final shift in my study, to include the human aspect of soil

management.

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Acknowledgments

I would like to firstly like to thank Nuffield Australia for the opportunity to grow as a person, a

farmer and a leader. This scholarship will leave an incredible legacy on both me and my family.

My investor Wine Australia has been incredibly generous and supportive in providing both the

funds and understanding for this program. They understand the value of focused investment

in human capital and its far-reaching effects.

I would also like to thank the Rathbone family and the team at Yering Station for the

encouragement, support and freedom to pursue the opportunity to garner such broad

knowledge. The vineyard and winery team also deserve thanks, particularly Rod Harrison and

Willy Lunn, for carrying the extra workload whilst I was overseas.

Mark Krstic for mentoring me though the research process, Scholar Liz Riley for working her

way through my early report and the countless farmers, researchers and industry folk who

opened their businesses for me during my travels.

Lastly, I would like to thank my wife Nami and children Mannus and Dulcie. They are the reason

that I am determined to be a better person and leader. It is much easier to be the one having

the adventure, than those who support us while we are away. For that I am forever grateful.

Abbreviations

SOM - Soil Organic Matter

CEC - Cation Exchange Capacity

Ca2+ - Calcium cation

Ca - Calcium

Ha - Hectare

Mg - Magnesium

Mg2+ - Magnesium Cation

Na+ - Sodium Cation

Al3+ - Aluminium Cation

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Objectives

The objectives of this technical report were to:

• Investigate and identify novel management methods for improving the long-term

sustainability of soil structure.

• Identify methods of encouraging changed practices regarding soil management in

farming operations.

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Chapter 1: Australian vines and soils

The Australian wine industry is large and diverse. 135,000 hectares (ha) are planted within 65

different regions, employing 172,000 people and including affiliated industries contributing

$40 billion to the Australian economy each year (Gillespie, 2015). It also represents Australia’s

fifth largest agricultural export by value.

Wine is grown in a diverse range of regions with varied climatic and geological areas, each

with their own challenges. Increasing climate variability is resulting in far more extreme

climatic conditions throughout the season. Periods of sustained, below-average rainfall, large

inconsistent rainfall events and heat spikes can all have deleterious effects on the vines and

subsequent fruit quality. It is the soil’s ability to handle these conditions, minimising abiotic

stress, that leads to a greater consistency of product between seasons and the long-term

sustainability of the vineyard, winery and industry. Australian soils are also highly varied,

though they are generally very old and fragile and often have pH, saline, sodic and structural

issues preventing the optimal exploration of the soil volume by vine roots. Many of these soils

were not prepared and ameliorated sufficiently prior to development and have suffered from

gradual decline due to the nature of vineyard management or should not have been planted

at all. Good soil management and healthy soils are important to reduce susceptibility to

climatic vagaries and to making the soil more resilient to weather extremes (Magdoff, 2000).

Grape production for wine is not a purely yield-based commodity, as the final wine quality

produced is equally important. The ideal soils selected are not required to be excessively

fertile as this impacts on the quality, though summer and autumn stress due to hot dry

conditions needs to be minimised.

In contrast to Australia, the European vine growing regions have far younger and resilient soils.

The French have centuries of experience and tenure with the land and time has allowed them

to learn which varieties and wine styles are best suited to their climate and soils. This is part

of the terroir of the region. They know that the heavier low-lying soils are best suited for

pasture, and the rocky outcrops are for forests or other agricultural pursuits. The sweet spot

between the two is where the vines are planted, and the very best is somewhere in the centre

of these plantings, such as the location of the Grand Cru vineyards of Burgundy.

While Australia has a significant history of wine production, there have been many vineyard

plantings in the last 30 years, (the total volume crushed has doubled in the past 20 years), so

the understanding regions is still developing in a global sense. Older plantings do give some

perspective on how soils can handle the traditional European farming methods first utilised in

Australia. The ability to innovate allows Australia an edge over Europe as Australia is not

bound by regulations of tradition such as those in Appellation dÓrigin Controlee (AOC), and

continued tenure will allow for greater understanding of the ground.

With tighter margins and falling productivity, it is tempting for the grower to chase greater

returns with the application of more fertiliser. This is a false economy, as the restrictions of

the vine’s capacity is a direct reflection of the soil available to the vine, not necessarily the

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amount of nutrient or water applied. Expanding or optimising the existing rootzone is critical

in the long-term sustainability and resilience of any terrestrial agricultural enterprise. The

reduced investment in soil amendments such as gypsum and lime are having insidious effects

on the soil and vine’s long-term performance.

What is the Problem? The ideal time to conduct remedial work on soil structure is during the development stage of

a vineyard. Deep ripping of soils, particularly down the future vine row, creates fractures in

the subsoil and provides an opening for the placement of ameliorant agents deep into the soil.

Permanent trellising and vines, with narrow spacings’ restrict the ability to operate large

earth-working equipment within established vineyards, so the physical remedial options

following vineyard development are far more limited, with more incremental gains.

Even after good remedial practices during development, conventional vineyard management

can lead to gradual decline in aeration and structure of the soil. The ideal vineyard soil is free

draining, with good water holding capacity, forming a naturally friable tilth when cultivated

and retaining soil strength of 1-2MPa when at field capacity (White, 2009).

Breakdown of soil structure leads to a reduction of vineyard physical function and then vine

performance. Smaller pores result in greater soil strength and anoxia, lower water infiltration

rates, lower hydraulic conductivity and poorer drainage rates, which all restrict root growth

and microbial activity. Once this damage is done, regeneration of organic matter within the

soil is affected and continual decline is inevitable (Cass, 2004).

The 3 P’s of Soil Management

Figure 1: The 3 P's of soil structure

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Soil should be treated like any living organism; it needs water, air and food to thrive and give

optimal returns. Soil structure and management is a highly integrated system, where each of

the main components influence all other parts of the living soil.

Maintenance, remediation and indeed destruction of soil structure can be reflected by three

key groups; pores, plants and people (Figure 1).

“Pores” describes the physical and chemical composition of the soils. This is the foundation of

the soil, the solid particles and the voids between them. “Plants” describes all biological

activity within the soil system, including plant roots, microorganisms, macro-organisms and

the carbon cycle. “People” describes the way we as custodians of the land manage these

ecosystems. Farmers have the ability in their management choices to influence the long-term

structure of these soils, for good and for bad, through the soil’s biology and physical state.

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Chapter 2: Pores

“Hard ground makes too great resistance, as air makes too little resistance to the surface of

roots” (Jethro Tull 1733).

“Pores” is a term encompassing the physical and chemical components of soil and indeed the

pores of the soil themselves. These building blocks are critical in the overall soil structure and

have formed through long-term processes during the soils development, which can make

successful remedial work difficult to achieve change.

The physical components of most soils are approximately 45% soil particles, 5% organic matter

and the remaining 50% a state of flux between air and water, depending on the soil’s moisture

content as seen in Figure 2 below. The size of the soil particles determines the soils textural

class and is a key factor in the pore distribution and subsequent soil structure. Coarser soils

will have far greater pore size, with a far reduced ability to hold water.

Figure 2: Distribution of solids, water and air within a typical soil

(Introductions to soils, 2006)

Soil physical components Soil structure is best described by the size, shape and arrangement of voids and pores, which

controls their ability to retain and transmit fluids and other substances and support vigorous

root growth and development (Bronick 2005). Structure is critical in providing habitat,

stability, air and water content for all living organisms within the soil its key components are

pores or voids, stable aggregation, and soil strength.

Pores vary in size and shape and provide the space for water and air to move (drainage) and

roots to grow. These are determined by the type of soil (clay, silt, sand, gravel), the climatic

conditions and the management practices. These factors also determine the amount of water

the soil can hold and the ability of the soil to drain. This drainage sucks air into the soil along

hydraulic pressure gradients, providing oxygen for the soil’s biological processes. Large pores

are free draining, though hold onto very little water and nutrient. Small pores drain slowly

and hold onto water very tightly. Many of the most resilient viticultural soils are a combination

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of pore sizes with varying particles sizes, such as those found in Corton Charlemagne in

Burgundy (Figure 3 below) and the first growth vineyards of Bordeaux.

Figure 3: Heavily tilled soils of Corton Charlemagne in Burgundy France (Source: Author)

Aggregates are secondary particles formed through the combination of mineral particles with

other organic and inorganic substances (Bronick 2005). This is the result of many different

interactions between the environment, soil management, biological activity, plant influences

and inherent soil properties. Aggregates occur in a variety of types and sizes. Stable

aggregation is the soils ability to bond into larger clods, resisting external forces such as wind

and rain to disintegrate and fall apart. Clay soils with less stable aggregation often tend to

have higher sodium cation ratios and be dispersive which means they lose all structure in

distilled water, and the clay particles become suspended in the solution (Magdoff, 2000).

Soil strength is a function of the soil’s bulk density and water moisture content. As soils dry

this strength increases as the soil will hold onto the remaining moisture tighter, binding the

soil particles more firmly. Pore size is critical in this function, as smaller pores will have greater

water retention and therefore soil tension due to the higher surface area to volume ratio of

the pores. Soil strength is also the soils ability to bear weight whilst wet without suffering

compaction. Sandy soils are the most prone to compaction, though all care should be taken

to drive on any soils when wet to avoid this.

Cation Exchange capacity Cation Exchange Capacity (CEC) is a measure of the soil’s ability to hold positively charged ions.

All clay particles and soil organic matter (SOM) particles have negatively charged sites on their

surfaces, which absorb and hold positively charged cations through electrostatic force. Many

nutrients in the soil critical for healthy plants exist as cations such as potassium (K), calcium

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(Ca), magnesium (Mg) and sodium (Na). In general, the higher the CEC the more fertile the soil

is as the clay particles retain more cations. As soils become more acidic these cations will be

replaced by hydrogen (H), aluminium (Al) and manganese (Mn) which are toxic to plants

inhibiting growth. Soils low in CEC often suffer from a deficiency in Ca and K which are critical

in healthy plant growth.

Sandy soils tend to have a much lower CEC due to the lower presence of clay and SOM. Figure

4 below shows a sandy duplex soil with clay at 40cm, clearly demonstrating the impact of SOM

in the top 10cm, and higher clay levels below 40cm on the CEC.

Figure 4: Sandy Duplex soil CEC readings. (Source: soilquality.org.au)

Each different cation has different properties and functions within the soil and can have a

profound impact on the soil structure. Cations which are polyvalent (multiple bond sites) such

as Calcium (Ca++), Magnesium (Mg++), Aluminium (Al+++) and Silicon (Si+++) have the capacity to

form much stronger aggregates as they can essentially create soil polymers by bridging

multiple particles together. Monovalent cations like Potassium (K+), Hydrogen (H+) and

Sodium (Na+) will produce a much weaker structure within the soil. Sodium is a problem in

many soils within Australia, leading to sodic and saline soils.

Calcium and Magnesium are both critical in creating well drained friable soil structure. Ca2+ is

however more effective in improving soil structure than Mg2+, as it is capable of inhibiting

dispersion of aggregates and can replace Mg2+ and Na+ within the aggregate, further increasing

stability. Mg2+ is more dispersive than Ca2+ and causes high swelling in clays, further increasing

disruption and dispersion of the soil structure (Zhang and Norton 2002).

Sodic Soils Sodic soils are soils that have greater than 5% Sodium (Na+) in all cations bound to its clay

particles. It is estimated that 27% of Australia’s total land area is affected by sodicity through

natural soil development (Northcote and Skene 1972), particularly in the more arid climates,

which are saline or sodic. The Na+ is a highly dispersive agent which directly breaks up

aggregates and indirectly degrades soil structure by limiting plant growth within the soil

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(Bronick 2005). Na+ bonds within the soil matrix are weak, particularly in comparison to

covalent cations. When wet, the exchangeable Na+ within the soil solution and clay particles

repel each other, amplifying dispersion. When the fine soil particles disperse, they reorientate

in solution and upon drying settle in a parallel structure, sealing the soil and preventing air

and water movement along with root development. Soils with high sodium levels are termed

“sodic” and are notable for a lack of structure. This settling often occurs upon a perched layer,

such as the soils B horizon, creating a hard “bleached“ layer (Figure 5).

Figure 5. A duplex clay soil in the Yarra Valley. Note the white bleached layer. (Source:

Mark Krstic)

Amelioration treatments Gypsum (calcium sulphate) is slightly more soluble than lime, and with adequate rainfall or

irrigation, releases calcium which can move readily into and through the soil profile. This

calcium displaces Na+ and Mg2+ from the soil, which are then leached out (Mikhail, 2010).

Gypsum is the most efficient and cost-effective form of applying calcium to the vineyard to

combat sodicity and salinity, though the incorporation of it into the deeper subsoil is difficult,

due to the high energy cost of deep ripping. Care must be taken post-application that the

released sodium can be leached adequately from the soil, away from the plant and irrigation

water sources. The uptake of this sodium can lead to significant physiological issues within

the vine and potentially to rejection of fruit at harvest due to exceeding sodium MRL’s for

export in wine.

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Another product currently being tested in several field trials around Australia is an

organosilicate compound called Aquasil, by CHT, a company based in Tubingen Germany

(Figure 6).

Figure 6: The picturesque town of Tubingen Germany is also home to CHT, trialling

organosilicate soil amendment technology

One trial objective was to reduce surface tension in dense soils, allowing for greater vertical

infiltration of irrigation water during summer. Early trials suggest this has occurred to some

extent though the most surprising result is the mobilisation of significant amounts of Na+. A

side by side trial on vegetable crops in Werribee found that it replicates the effects of gypsum,

though at a much faster rate. Na+ was mobilised and leached from the system within one

growing cycle in vegetables, whereas the gypsum achieved similar results but took several

growing cycles. These trials continued during the 2017-2018 season in multiple crops and

regions within Australia, including collaboration with Monash University in Melbourne,

Australia.

Salinity Further areas have been affected by salinization, through perched water tables, dryland

salinity and saline irrigation water. Salinity is more of a problem in arid areas, below 500mm

annual rainfall, as there is not sufficient rain to flush salt out of the soil profile. These soils

also tend to be more alkaline than those in the higher rainfall areas along the coast where

there is adequate clean irrigation water or rainfall; alkaline soils can be corrected through

leaching and flushing of the Na+, however there will have been some damage occur already

due to dispersion.

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Figure 7: Checking perched water table levels in Almonds in Helm, California (Source:

Author)

Irrigated areas of inland Australia and the Central Valley of California both face issues with

perched water tables. Large low-lying areas of the valley are now being bought back from the

landholders for environmental purposes at great cost to government. The expansion of

irrigated agriculture utilising saline water and the move from flood irrigation to micro

sprinklers in almonds in the central valley has seen some plantings facing significant losses due

to salt damage. Despite the deep sandy soils in the Central Valley, in some areas an

impermeable clay layer, well below the soil surface, has created an underground pond with a

high salt concentration from salty irrigation water and evapotranspiration. Figure 7 above

shows the checking of the water table prior to irrigation. The salty water is a major chemical

inhibitor of root development, again creating a shallow root system. Care must be taken on

these soils to ensure that the irrigation water applied is not so great that the draining irrigation

water mixes with the underlying perched salty water. If water mixing occurs then the salty

water will start to move up through the profile through osmotic pressure, increasing sodium

at the shallow depths and further disrupting soil structure. Short regular bursts of irrigation

18

are required, rather than long intermittent cycles. When water is supplied on a rolling

schedule, such as through an irrigation district where water may be allocated one day per

week, the plants will suffer significant stress before their next irrigation. The long-term

viability of the soil and productivity of these systems must be questioned.

Physical treatments Mounding is the working up of midrow soil into a friable tilth which is then pushed under vine

using a mounding blade, creating a “V” profile in the soil. The total amount of topsoil within

the vine row is the same, however the depth of soil at the vine is significantly deeper as seen

below in Figure 8. In sodic and saline soils this can create a greater volume of soil around the

dripper zone where most active roots are away from any perched Na+.

The V-shaped profile also creates a central furrow which can aid in drainage, allowing the Na+

to drain free of the active roots, reducing uptake of the sodium into the plant tissue. An added

benefit is reduced asphyxiation of roots during winter and wet springs.

Figure 8: Mounding of a vineyard in the Yarra Valley. The permanent sward hides the

slightly sloping channel through the middle of the block. (Source: Author)

Tile drains are often used in areas of salinity to assist in the removal of excess Na+ from the

block during the wetter months. “Drainage tiles” are agricultural drainage pipes which form

a network of drainage line “criss-crossing” across the paddock. Pipes are placed into a trench,

and backfilled at the desired depth of drainage, often either just below the desired root zone

or on an impermeable subsoil layer where salty water may perch. The underground water will

drain into these pipes and flow down a gradient to an outlet point of the system - a drainage

channel - to collect these salts. Care must be taken that this outlet channel is not going to

contaminate fresh water supplies such as dams or water courses as the solution which drains

19

will be high in sodium. Examples such as those in the lowest points of the Central Valley of

California, where there is no gradient to move sodium away makes these soils unviable.

Another advantage of drainage is the ability to remove excess water from the soil profile. Not

only will this increase strength in wet soils, reducing pressure on the clay soils to disperse, but

it will give plant roots the available oxygen they need to thrive early in the season when soils

would otherwise be saturated. Water and oxygen together are required, not water alone, to

produce a thriving root system.

Acidification Soil pH is a function of free hydrogen cations within the soil system. Grapevines, like most

plants, thrive when soil pH is in the range of 6-8, as this is where the availability of most key

nutrients required for plant growth is at its optimum. Figure 9 below shows many soils in

Australia are highly acidic (such as the duplex loams of the Yarra Valley), or alkaline (the soils

following the Murray River), shifting this nutrient availability. In acidic soils, subsoils are often

of a lower pH again, regularly well below pH 5. As pH decreases, H+ concentrations increase,

leading to the breaking of the ionic bonds on large cations in the soil such as aluminium and

iron (Fe3+) and mobilising them. Al3+ is a chemical inhibitor to vine roots which will terminate

at this horizon and not explore the soil below. As most microorganisms and plants struggle to

thrive in low pH soil, soils can remain bare and exposed to environmental degradation. Often

it is only the weed species tolerant to such acidic conditions that can thrive.

Figure 9: Soil pH in Australia (Department of Environment, 2010)

20

Farm management practices can lead to acidification of soils over time. Fertilisers such as

synthetic urea, or large volumes of chicken manure, will lead to a decrease in soil pH.

Broadacre farmers in the Pallouse, Washington State of USA, who had been growing cereal

crops on deep soils with natural pH of 8 and above, are now facing significant issues with

acidification. Common practice in the area is to apply significant amounts of urea when

sowing their crops. Decades of this practice has seen the pH of their topsoil fall to 4.6 and

below.

The effect of low pH on soil structure is complex. Low pH can result in greater dispersion in

clay soils. due to the removal of large cations from the soil matrix, leading to smaller soil

aggregates and a greater repulsion between particles. Low Ph disrupts the level of nutrients

available, binding up many micronutrients such as Molybdenum and Zinc, whilst making large

amounts of toxic Aluminium available to the plants. The cumulative effect is lower levels of

root growth and microbial activity, resulting in fewer root exudates and polysaccharides in the

soil, which help in binding soil particles and creating more stable aggregates.

Chemical ameliorants Lime (calcium carbonate, Ca(CO3)2) contains 40% calcium and is essentially insoluble in water.

It is an alkaline form of calcium which is beneficial in increasing pH and providing much needed

calcium to improve soil structure. The low solubility of lime means that the finer the product,

the quicker it will dissolve, and the more effective it will be in reducing soil pH. The acid in the

soil reacts with the carbonate in solution, releasing the Ca2+ which will then displace Na+ and

form much stronger soil aggregates. The rising pH will also provide greater nutrient availability

in acidic soils as the pH gets closer to neutral. This is a very long-term approach, as any

changes in soil pH are slow to occur. Lime is not effective in adding calcium to alkaline soils as

it is completely insoluble in this environment.

Long-term lime trials in Tasmania have seen continued increased productivity 20 years after

initial application of lime on pasture (Krstic, 2017) (Figure 10), yet in the Pallouse there is

currently no demand for the application of lime to alleviate this issue, as there is no local

supply. If the acidification continues, these farms may be unsustainable due to declining

productivity and profitability. It was staggering to see the degradation of these soils, and at

some point, the investment in de-acidification practices must occur for these fertile soils to

remain productive.

In soils with a low Ca:Mg ratio, care must be taken to ensure that the applied agricultural lime

is coming from a source of high calcium purity. Dolomite, a form of lime, (magnesium

carbonate, CaMg(CO3)2) is also effective at reducing the pH and does provide some calcium

(25%) along with Magnesium (11%). H+ and Na+ will be displaced from the clay lattice;

however, the presence of Mg may exacerbate any issues with high magnesium ratios in the

soil.

21

Figure 10: Spreading gypsum and lime in the Yarra Valley in Autumn (Source: Author)

Cultivation Cultivation is a common practice in European and North American vineyards for a variety of

reasons, including weed control and water-use efficiencies as can be seen below in Figures 11

and 12. The soils in these regions are far younger and less weathered than in Australia,

resulting in them having much better structure, larger stronger aggregates, and often rock

particles which can all reduce coalescence and dispersion. Emanuel Bourgignon, a soil

scientist with LAMS in Burgundy France, who has spent significant amounts of time in

Australia, was adamant that cultivation should not be the preferred soil management tool in

many of our soils. This is a view shared by many local soil scientists.

22

Figure 11. Professor Pilar Baeza of Madrid Polytechnic in heavily cultivated Grenache

vineyards of La Mancha Spain (Source: Author)

Cultivation is still utilised in some vineyards of the warmer areas of Australia as a way of

reducing water use by mid row plant species, though it tends to be utilised less and less. The

turning of the soil exposes soil organic matter (SOM), previously bound within soil aggregates,

to oxygen, allowing for the rapid expansion of microbial activity and the oxidation and loss of

this previously stable carbon. The nutrient bound by this SOM is mineralised, giving the vines

a short-lived boost in vigour and health. Even with consistent re-sowing of annual crops

including legumes, over time a gradual reduction of overall SOM results, compared to a

permanent sward. Ironically, this will reduce the amount of water the soil is able to hold,

particularly in sandier soils. Continued cultivation has a detrimental effect on both the “Pore”

and “Plant” aspects of soil structure.

23

Figure 12: A heavily cultivated midrow and undervine area in Rutherford, Napa Valley,

California (Source: Author)

Tilled bare earth is prone to degradation by rainfall events, as the aggregates have been

disrupted, exposing the bare earth to greater dispersion by the force of the raindrops. This

causes poorer infiltration in heavier soils, as pores and bio-channels are disrupted. Higher

runoff may result, resulting in the loss of topsoil, or the vines may not be able to utilise all the

rainfall during the warmer months, when the water requirements are at their highest.

Compaction Compaction has major effects on the ability of the plant to grow and thrive. Compaction is

generally due to the operation of heavy machinery on wet ground, when the soil strength is

reduced. The downward pressure from the weight of the tractor forces the soil particles

24

together (Figure 13), decreasing the size of the soil pores. The effect is most noticeable in

sandy soils. Continual cultivation can also lead to compaction, as the underside of the plough

cut will develop a hard pan over time if not remedied. This compacted layer acts as a physical

inhibitor, causing increased soil strength, reducing infiltration and root penetration, even

when the soil is moist. Mouldboard ploughs have been used in vineyard development in the

south of France to invert soil during vineyard development. Subsequently, a hard compacted

layer forms under the weight of the tractor and plough share in wet conditions, causing

stunting of vines and lost production (White, 2009).

Compaction also has an indirect result on plant growth. When roots push up against a hard

mechanical barrier in the soil, either compaction or rock, there is a hormonal signal sent to

the shoot to slow down growth. This is a survival mechanism for drought-like conditions; since

soil drying coincides with soil hardening, it is very difficult to differential between the effects

of compaction and drought.

Figure 13: Tractor tyre marks in a cultivated vineyard in Champagne, France (Source:

Author)

25

Deep Ripping In traditional best practice viticulture, deep ripping is undertaken pre-planting to ensure the

best conditions possible for the development of young vines. Deep ripping, or subsoiling, is

the disturbance of soil levels down to 100cm by tynes with wings or points attached. This

procedure needs to be carried out in summer or autumn, as the soil moisture content must

be right to ensure the shattered soil leaves fissures that intersect at the soil surface; too dry

and the ground, particularly heavier clay soils, will be too difficult to penetrate. In wetter

conditions the blades will smear the underlying soil, creating artificial barriers which will be

more restrictive than the original soil (White, 2009).

The average vineyard row width in modern viticulture is below 3m, with some as narrow as

1m. The tractors required for best practice ripping are too big to be utilised in established

vineyards to the depth of 1m. Smaller rippers can be utilised on conventional vineyard

tractors, although the depth of shatter will be less.

Planting replacement vines in high density established vineyards in Burgundy is facilitated by

the use of auger drills mounted on these specialty tractors. The pilot hole for the new vine

gives adequate soil disturbance, even with the competition of the established vines, due to

the fertile free draining soils present.

Care must be taken following ripping to not travel on the rip lines for as long as possible.

Plastic clay subsoils will tend to reform into their massive structure if driven over while still

moist; time must be given for plant roots within the vineyard system to penetrate the channels

before this can occur. In new developments repeated passes of equipment during trellis

instillation have the ability to undo all of the ripping benefits, if undertaken when the soil is

too wet.

Another concern with deep ripping established vineyards is the effect of root pruning vines.

Trials in the Barossa Valley found reductions in vine capacity lasting several years following

ripping too close to the vines in every row, due to the reduced root structure.

Controlled Traffic Like the closing of rip lines when driving on them, compaction of soil in general is most

probable during early spring, when soil is moist and tractor operations such as spraying are

regular.

26

Figure 14: Specialised over-the-vine tractors and multiple row sprayers are vital in close-

planted vineyards in Burgundy, France (Source: Author)

Modern advances in vineyard equipment (Figure 14 above) and trellising have allowed for far

more efficient spray management practices with multiple row sprayers. This gives the

manager the ability to create travel rows, in every alternate row, whereby the same rows are

driven each time a spray operation is carried out. The travelled rows become compacted,

whilst the alternate untravelled rows have reduced compaction risk and pressure. This can

provide a greater volume of soil for the vines to explore and reduce the stress on the vines,

whilst also significantly improving vineyard efficiencies. In regions such as Bordeaux,

Burgundy and Champagne, where row spacings are narrower, the effect is greater, as the tyre

contact zone is a higher percentage of the total row width.

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Chapter 3: Plants

The soil food web This function of soil structure management encompasses all living organisms within the soil,

including plants, bacteria, fungi, arthropods, and earthworms. These organisms all form part

of the soil food web (see Figure 15 below), which is the cycle of life when breakdown of all

carbon-based plant residues from waste, root exudates, mulch or other soil organisms occurs.

This breakdown of organic matter presents an opportunity to deliver greater volumes of SOM

naturally, deeper and without disturbing the soil, and is mostly due to the breakdown of root

material. This process is often referred to as bio-drilling which is the utilisation of biological

practices to create fractures, channels and pores within the soil structure and all parts of the

soil food web contribute to this process.

Figure 15: The soil food web (USDA, n.d.)

Biological activities are inherent in all soil types, even the most inhospitable. It is estimated

that each gram of soil contains over 1 million different microbial species, of which only 10%

are currently known.

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Microbiological activity When plants are actively growing they are continually exuding carbohydrates into the soil

through their roots. This, along with other forms of carbon within the soil from decomposing

roots, compost or other plant residue, creates a food source for fungi, bacteria and

actinomycetes, allowing their populations to thrive. These organisms are the start of the food

chain, providing food for larger organisms both above and below ground.

Fungi and bacteria species are highly sensitive to conditions within the soil regarding their

ability to thrive. Like all living things they require nutrients, water and air, so the ideal soil

structure will display increased soil microorganism activity. Prolonged periods of dry bare

earth, repeated tillage or consistent waterlogging will have a deleterious effect on these

populations. Fungal colonies will utilise their hyphae to bind soil aggregates together, reducing

soil strength and increasing water infiltration. Bacterial colonies will exude glue-like

compounds which also aid in the formation of soil aggregates. An active and stable fungal and

bacterial biomass will also find a balance capable of helping to inhibit or compete with soil

borne pathogens. As this biomass grows, it increases the SOM and the soil’s water holding

capacity and CEC.

There is a growing belief that the health of the soil’s microbiology is directly correlated with

how quickly they can respond to stimuli when coming out of a dormant state. Trials where

dry soil samples have water added, show that the more resilient soils with better productive

potential will quickly develop respiration levels much higher than poor soils (Haney, 2017).

The key to maintaining a resilient microbial population is to retain living roots, and hence a

food source, within the soil.

Figure 16: Rick Haney, USDA in Temple Texas with his equipment for measuring soil

respiration (Source: Author)

29

Earthworms and arthropods Of the larger soil born organisms, earthworms and arthropods such as beetles, are the most

prevalent. Arthropods tend to be situated closer to the surface, shredding plant residues and

feeding on other soil organisms. Earthworms, of which there are many different species, tend

to fall into two categories, composter and earth-worker worms. Composter worms are not

suited to survival in the soil but feed on organic materials, rapidly breaking this down and

creating large amounts of vermicompost or vermicast. These castings have been shown to

stimulate plant growth and can improve soil structure (Buckerfield, 2001).

The earth-worker worms are more valuable as they tend to move vertically through the soil

and can transport applied ameliorants in their gut deeper into the soil. This is particularly

useful for substances such as lime and gypsum, which have low solubility and can take large

periods of time to incorporate into the soil. The worm castings deposited during this

burrowing also stabilise aggregates, and the channels aid in drainage, root penetration and

water infiltration.

The best way to optimise earthworm populations is to get the largest amount of plant biomass

above and below ground, and there are various management practices that can achieve this.

Cultivation is detrimental to working populations, destroying habitat even post cover crop

production, so permanent swards are of greatest benefit. Mulch and compost undervine can

have dramatic effects on the presence of worms, as they reduce the variability of temperature

and moisture content in the soil. Lime applications have an added benefit of boosting worm

populations, as earthworms do not survive as well in acidic soils (Buckerfield, 2001). This is

part of the reason why many farmers and researchers are now using earthworm counts as

method of monitoring soil health trends, though actual count numbers can vary depending on

the climatic conditions at the time.

Root structures All plant root structures are defined by the availability of water, space and nutrient available

to them. Compaction, coalescence and dispersion will create much smaller pores, increasing

soil tension and making the soil less hospitable. Recent research suggests that vines only have

a single flush of root growth through the season. This is primarily in spring (Laura Radville,

2016), so this time is crucial in having the soil in a state with minimal restrictions for growth.

Soil tension higher than two megapascals will create a physical inhibition, shortening roots

and preventing penetration, which in soils with high soil strength can be soon after the soil

starts to lose moisture. It is therefore crucial that the winter period is utilised to create diverse

and permanent rooting structures to help form aggregates and other fissures in the soil

structure, reducing soil strength and creating channels for vine roots to penetrate.

Midrow Management Permanent swards are possibly the best way to develop stable structures and aggregates

within the topsoil. These can be grown out in spring, utilising excess moisture from the soil,

30

then slashed and thrown undervine, creating a layer of mulch to help build up undervine OM.

Ryegrass is especially effective in creating a large biomass within its fibrous root system,

though this is relatively shallow. Lucerne would be a great option in trying to get roots deeper

into the profile, however it is difficult to establish in a vineyard situation and will compete with

the vines for water and nutrients during the growing season. Clover, vetch and other legumes

are good to include for diversity in both flowering and vegetative bodies and rooting

structures. Rick Haney and Frederic Thomas and others are promoting biodiversity in plant

species as a major contributing factor to improved soil structure and health. Many of the best

vineyards in Burgundy would have a diverse range of vineyard floor plants prior to cultivation

back into the soil. An added benefit of a diverse sward species is that, when grown out in

spring, it creates different habitats for beneficial insects close to the main crop. Additional

winter annual crops can also be direct-drilled into the sward in autumn to supplement the

prevailing species, further diversifying the seed bank present.

Figure 17: Bob Schindelbeck of Cornell University with Bruce Murray of Boundary Breaks

Wines, Finger Lakes District NY (Source: Author)

Large taproot species, such as radish, can be utilised to try to break up the soil profile allowing

cavities for subsequent roots to penetrate. Radish is a winter active species in Australia,

producing most of its bulk vegetation during these months. In North Western USA, it is grown

in autumn, to break open soils in broadacre agriculture, prior to the winter freeze which then

31

kills the plant. Bob Schindelbeck (Figure 17) of the Cornell University Soil Health Laboratory

in New York State is another advocate of building soil health through cover crops and reduced

tillage. Bob and his team found that the growers who used and demonstrated the use of tillage

radish prior to winter improved trafficability, water penetration and overall yield the following

year. The large taproot was also significant in that it sparked the grower’s imagination to what

could be achieved in the soil, a lightning rod for the spark of change.

High soil strength in dry clay loam soils during autumn seeding in Australia severely limits the

radish’s ability to penetrate deep into the soil profile. However, if the soil tension is too high

below 5-7cm it can cause the tap root to move laterally rather than down into the profile.

Figure 18: The effects of soil strength on tillage radish grown in the Yarra Valley, Australia

(Source: Author)

The image on the left in Figure 18 shows the lateral movement due to mechanical resistance

during autumn (The radish on the right of each image is germinated in a softer moister soil

hence has better penetration). The image on the right is of a self-sown radish growing under

drip irrigation through summer. Despite sufficient water and nutrient, the radish was still

forced to grow aerially.

The channels opened by the radish’s vertical growth provides aeration for the soil, allows

deeper irrigation and root penetration. As it decomposes, it provides a source of carbon for

microbial proliferation deeper into the soil which cannot be achieved through shallow rooting

grasses or application of surface compost. The lateral expansion of the radish also causes the

soil to crack, creating more fissures at the surface for root exploration and water infiltration.

32

Undervine management One of the greatest opportunities for improvement in soil structure undervine may lie in the

utilisation of vegetation in this strip. During the growing season, undervine vegetation can

prove detrimental as it can be a limiting factor in productivity, competing with the vines for

water and nutrient, particularly if water supply is limited. The winter months when grapevines

are dormant is a great time to generate root systems and channels in the undervine area.

Trials in the Yarra Valley in 2017 found that under vine seeding during autumn following

substantial irrigation has seen much better penetration of the tap root (Figure 18) as the soil

strength has been reduced earlier in the radish’s life.

Undervine vegetation can then be chemically controlled at the commencement of the season

or mown low with specialised equipment to keep the vegetation alive but reduce the

evapotranspiration and hence water consumption during the season. Chemical control should

only be carried out when vegetation is present to prevent spraying bare earth allowing the

killed plants to form a mat of decomposing mulch, protecting the soil from the elements.

A significant issue in vineyards which have high herbicide usage and undervine cultivation is

crusting, which is the result of dispersion of bare soil by rainfall at the soil surface. If no

vegetation is present, aggregates are exposed to dispersion, causing the settling of the fine

clay particles. This settling results in a dense layer of particles, forming a crust which makes

plant germination and water infiltration more difficult. Cover crops and even weeds can

struggle to germinate and increased rainfall runoff can be a consequence.

Mulch and Compost Mulch and compost are used for a variety of reasons, including soil moisture retention, cooling

of soil, building SOM, and improving soil structure. Various mulching media have been utilised

and trialled and the cost is often dependent on the quality and source of the product. Mulch

tends to be a raw product such as straw, with a high carbon content and has the capacity to

draw soil nitrates away from the vine as it decomposes. It tends to be banded undervine,

providing protection for the soil from the environment. Compost is a mix of raw materials

that has been through the composting process so is stable from a nitrogen perspective and is

high in microbial activity. This can be either banded undervine, or broadcast as a general soil

conditioner.

Cover crops can be utilised as a form of mulch. Grass and legume species which produce high

levels of bulk organic matter, such as ryecorn, and oats can be grown out to maximise plant

biomass, then slashed undervine during spring or rolled and crimped to create a mat of straw

in the midrow. Straw and leguminous crops will decompose rapidly, due to the high amounts

of simple carbohydrates in the plant, particularly when sufficient N is available. This

decomposition process results in an increase in soil aggregates, as they are formed by soil

organisms during decomposition (Magdoff, 2000). Woody material and compost is more

33

stable and is less likely to decompose because the carbon is held in more complex and less

soluble compounds, such as lignin.

Surface-applied compost can be effective in reducing soil moisture loss and minimising weed

growth, however the greatest benefit for soil structure is gained when the compost is

incorporated into the soil. The incorporation of compost has been shown to produce long-

lasting benefits in pore size and distribution, which has flow-on effects for biological activity,

water holding capacity, infiltration, aggregate stability and aeration (Cass, 2004).

The critical factor in this is the disruption to the soil’s preference to coalesce. Wet soils want

to settle to form stronger, more massive structures, and each movement of a tractor over the

soil is adding to this. Compost, being a stable form of carbon, provides a bonding element for

the soil particles and it helps reduce soil strength by creating planes of weakness within the

soil. The greater distribution of larger pores then provides greater pore continuity, aiding root

penetration of vines and other plants within the vineyard environment. Microbial activity will

also follow the introduction of compost material and root structures, amplifying the benefits

of the compost addition. The increased number of pores also improves the amount of oxygen

available to the roots and microbial population in the topsoil. Subsoils do not appear to

respond as well to the addition of compost due to the anaerobic nature of subsoils. Compost

is also difficult to apply to the subsoil, but when added to clay subsoils to improve the CEC,

drainage and microbial activity of the soil has often been sealed over by the plastic subsoil.

This process encloses the organic material and excludes oxygen, preventing decomposition of

the OM.

Mulching material should be accessed from nearby if possible to reduce transport costs. Straw

can be a by-product of cereal crops or cut hay from pasture and vacant land. Many of the

warmer regions of Australia are within the cereal growing areas, though access to the straw

can be variable. Winery-owned vineyards can reduce their waste and utilise the grape skins

and stalks, cardboard and other waste products to form the base of a very efficient compost.

34

Further materials such as straw, wood chips, and manures can be sourced from nearby and

added to provide greater diversity in carbon sources.

Figure 19: Natural Selection Farms composting facility in Washington State (Source:

Author)

Natural Selection Farms is a diversified organic farming operation based in Sunnyside,

Washington State USA. They have developed a compost business (Figure 19), recycling waste

products from their own farm and other local businesses as well as municipal waste. This has

provided their own operations and community with a cheap reliable source of compost,

diversified their business interests and solved an issue for the community in dealing with

waste products.

Vine Roots Vitis vinifera is the traditional winemaking grapevine species in the world and each different

varietal, such as Chardonnay, Shiraz, Sangiovese and Grenache, all belong to the same species.

There are hundreds of other Vitis species in the world which have different growing natures

and are bred and utilised as rootstock for a myriad of purposes.

Each rootstock has its own different characteristics. Some like 101-14 are more prone to

having shallow fibrous root systems and are more susceptible to water stress. This is effective

in controlling vigour on vigorous high capacity soils, though in restrictive soils it may not work.

When soils have poor structure the 101-14 vines struggle to extract water during the summer

months and irrigation is often not sufficient to keep the vines from stressing. It is possible that

this is due to the roots spending large amounts of time in wet conditions during spring, subject

to various root rots, then struggle to penetrate and extract moisture during the warmer

months as soil strength increases.

35

Others are more drought tolerant and push roots deeper into the soil, rather than having a

large collection of fibrous roots close to the surface like Paulsen 1103 or Richter 110. Some

rootstocks like Ruggeri 140 are also far more salt tolerant and can exclude salt from the soil

solution when extracting water (Dry, 2007).

In Australia, most plantings are on V. vinifera roots, though some individual areas have reasons

such as increased yield or biosecurity (phylloxera and nematodes) for planting on other

rootstock. The cost of ungrafted V. vinifera planting material is 20% of the cost of grafted

vines on rootstock, so the economic incentive to plant on rootstock needs to be strong.

Biosecurity is the primary reason for choosing different rootstock within all the USA and

Europe as Phylloxera is endemic in these areas. Beyond biosecurity, the decision making

around rootstocks is geared toward salt tolerance or water use efficiencies. In Europe, tight

AOC controls mean that planting different varieties in certain regions is impossible when trying

to mitigate against climate change. As a result, rootstocks are the way forward in trying to

extract more drought tolerance and delayed ripening in these areas (Ollay, 2015).

36

Chapter 4: People

“The eye sees only what the mind is willing to comprehend” Robertson Davies

Soil is slow to form, taking tens of thousands of years, and improvements in soil structure can

take significant amounts of time, though their inherent characteristics are not likely to change.

Farmers’ management practices can profoundly affect the long-term viability of soils

productivity; however, these practices form the third function of managing soil structure. Soil

ameliorants, tillage, and traffic management are all tools to use in the management of soils

and each soil has its own unique characteristics which need to be addressed. The question for

each farmer is the reason these practices are undertaken and are these the best practices for

the long-term sustainability of the soils. Further adding to the complexity of this decision-

making process in the wine industry is the need to find the balance between productivity and

wine quality outcomes.

Change limiting factors The soil research community has long been advocating the virtues of the structural health and

various remedial techniques, with varying degrees of uptake. Practice change and adoption

of techniques and technology takes time. The innovators and early adopters pave the way for

the majority and there will always be the laggards who resist the change. The Robertson

Davies quote above “The eye sees on what the mind is willing to comprehend” was shared by

Jim Kamas of Texas A & M whilst discussing the need to adapt practices in the Texas Hills

Country wine region. Change will occur when the grower is ready.

There are countless examples of successful changes through agriculture, such as the no-till

and traffic management approaches to broadacre farming, and micro-irrigation systems

replacing flood irrigation practices in irrigated crops. There can be significant barriers to

uptake of these changes such as insufficient resources. Many agricultural enterprises are

financially stretched and time poor, and often do not explore networks which can deliver new

innovations to their business. Many practices that can deliver change to a business are not

capital intensive, so often the biggest resource required is the energy required to change

mindset.

Agricultural risk plays a role in the adoption on new methods of farming. The risk associated

with climatic conditions and to a lesser extent market factors are uncontrollable yet present

with each crop. Soil structural management is a long-term approach which is difficult to

measure and does not deliver immediate results, so the feeling of reward for effort can be

elusive. This lack of reward for effort can often result in practices abandoned at the start of

the journey. A sown cover crop may fail due to insufficient or excessive rainfall, and the farmer

may feel that the time and resources used were not worthwhile and do not persist with the

practice. Innovative crop protection methods may be perceived to be not worth the

investment if undertaken in a low disease pressure year, not understanding the full benefits

may be realised in a high-pressure year. Mulching can see similar outcomes. The use of straw

37

mulch can provide habitat for many forms of organisms. This is one of the benefits of mulch,

as discussed earlier, however sometimes these organisms can be detrimental to the crop. One

wine producer in the Willamette Valley in Oregon abandoned the use of straw mulch following

the discovery that it provided habitat for rodents. Mulch was banded under-vine, surrounding

the vine trunks, to retain moisture and build soil structure. These rodents whilst sheltering in

the straw mulch found that the young vines were a great localised food source, and the death

of large numbers of vines resulted. Whilst the losses accrued were devastating for that young

block of vines it appears that older vines are not subject to this sort of damage. It is unknown

if this was a seasonal problem, with a year of high rodent numbers causing the problem, as

the practice was abandoned without further trials.

Other farmers in the Barossa Valley in Australia found that if they mulched their vines during

the season, earwig infestations were reported, resulting in fruit quality downgrades and hence

lower returns per tonne. It is not known if the same gains could be made in water use

efficiency and soil improvement, and the earwig issue be resolved if the mulch was kept away

from the trunk of the vine. Research needs to be done to determine if there is a way to modify

these practices to get the long-term results and eliminate the negative attributes.

All trials or operations which have not been deemed successful should be examined to

elucidate the cause of the response. By continually questioning the cause of the failure, the

trial may be improved by using an alternate strategy and the gains may be even greater. The

road to improvement is not clear, and many hurdles need to be cleared along the way.

Lack of champions One way of promoting greater uptake of innovations and technology is through the active

work of farmers acting as champions for change. Farmers are far more likely to adopt new

practices if they can see something in action, ask questions and gain a greater understanding

of the process through product testing. It is this practical demonstration and understanding

that presents the greatest opportunity for change. Many other agricultural sectors are much

better than the Australian wine industry at sharing new innovations and ideas.

Focus groups such as the “discussion groups” in the Irish dairy industry, sees small network

groups of farmers walk each other’s farms focussing on a relevant topic. A follow-up meeting

is scheduled the next week to give the visiting farmers a chance to provide positive

constructive feedback and give their own farm reports, benchmarking themselves against

industry standards (Rushe, 2017). There is a “Chatham House rules” approach ensuring

transparency of the businesses; nothing is immune from discussion, including some financials.

Whilst these networks are small, and the reach is limited, it shows community engagement

and continual improvement. Many farmers are also part of several groups, so the learning

from one farmer is capable of diffusing though a wider audience. One of the issues we could

have discussed within the wine industry is the large number of absentee owners. Farms are

left to be run by managers or contractors without the presence of the owners and if employee

38

turnover is high, there is no consistent long-term view to what success in soil management

looks like. It is important that, as an industry, learnings are shared as widely as possible.

The role of the champion needs to be truly authentic in sharing failures as well as successes to

ensure the full benefits are spread to the community. In advance of the removal of milk quotas

in the EU, the Irish dairy industry recognised there was no example of large scale, greenfield

dairy developments within the country. A joint venture was established between Glanbia PLC

(the largest milk processor in Ireland), the Irish Farmers Journal and the Irish farmers

themselves. A long-term lease was obtained on 117 Ha of farmland, and a fully operational

commercial dairy was developed three years prior to the removal of the quota system. The

goal was to run this dairy to best practice standards, fulfil all regulatory obligations and report

to the industry with full transparency on operating efficiencies. Having the Irish Farmers

Journal as a partner gave the operation the opportunity to communicate its successes and

shortcomings with far greater scope and depth of content. By developing this demonstration

site in advance of the boom in greenfield developments, the industry could become aware of,

and manage many issues that were common in these ventures. A secondary benefit was the

effect on regulations, as the farm was not able to cut any corners in the way it conducted

business. This clearly showed where regulations were having detrimental effects on the farm’s

ability to make gains in productivity or profitability and formed a valuable reference point

when the industry was pushing for change (Rushe, 2017).

The soil acidification in the Pallouse region of Washington state is an example of both positive

change and the lack of champions willing to promote different approaches. The deep fertile

soils are on rolling swales of land, and years of mouldboard ploughing had seen the soil all

moving from the crest of the hills down into the valleys. This was further subject to erosion,

which was clogging waterways and reducing productivity on large portions of the higher

ground. The introduction of no-till farming reduced erosion, built soil structure and utilised

rainfall much better due to the increased rainfall infiltration with lower runoff. This was a

great result and an example of positive change.

The continual use of this practice, in conjunction with synthetic fertilisers, has now seen a

narrow band of acidification form. A pH of 4.6 is very low, and if this were to continue its

downward spiral the soil would become irreparably damaged.

39

Figure 20: Measuring Soil pH in no till soil in the Pallouse, Washington State (Source: Author)

Despite the USDA soil scientists insisting on the virtues of lime application, no farmer was

willing to take it on board. There were many reasons - the lime was not local, the cost was

perceived as too high, and the yields were still good. The potential cost of not carrying out

any remedial work could, however, be devastating in the future. Both USDA soil scientists and

extension officers believed if a suitable farm trial or champion could be demonstrated, uptake

would be much higher.

Frédéric Thomas, a French farmer and editor of TSC magazine, is a champion of conservation

agriculture. Like Rick Haney, Bob Schindelbeck and numerous other soil scientists, he

advocates the use of cover crops to regenerate soils in broadacre farming. The language that

Frédéric is able to use due to his practical farming experience allows for his message to be

shared authentically, with a greater uptake and acceptance of the message than perhaps even

the best research communicators.

40

Figure 21: Frederic Thomas at a grower field day in Effiat, France 2015 (Source: Author)

Successes can inspire action, however if the next farmer does not experience the same levels

of success for any reason – timing of treatment, seasonal conditions or lack of resources –

then the treatment may be abandoned prematurely, or, at worst, the farmer may be forced

out of business. The remaining farmers then enter the “once bitten twice shy” phase.

The role of any form of improvement needs to be continuous and as such there will always be

advances and failures, but the dialogue needs to be ongoing. If a community of trust can form

around the champion, then the learning will be far greater and longer lasting.

41

Conclusion

The current fiscal conditions of the wine industry are not those that promote large amounts

of investment back into the vineyard. Many gains can, however, be made through better

management decisions with minimal investment. Controlled traffic and less cultivation,

allowing undervine growth, requires fewer inputs and is a more hands-off approach. The gains

are incremental and difficult to see from season to season, particularly as seasonal variation

in temperature and rainfall is an even greater influence on growth and abiotic stress, though

long-term trends will develop.

It is important to work within the season and long-term climatic forecast in determining the

best management strategies in any one season. Dry winter forecasts may not warrant seeding

new species in the midrow or undervine. However, investing in mulch or compost may see

returns in increased yield and quality, as well as the long-term soil structural benefits this

brings. Wet springs require minimal tractor operations to reduce compaction. The response

to the climatic risk of the season is critical in optimising soil structure as a poor decision is

often more influential than a good one.

It is critical that farmers continue to try new techniques to continually improve and

understand that not everything trialled will be successful. Trials must be questioned, like every

operation within the business, to understand why it has failed to determine the greatest

lessons and ‘where to’ from there.

The wine industry is largely a brand-driven industry, as opposed to a commodity, that spends

large amounts of time and resources engaging with consumers, trying to gain an edge over

competitors. The number of variables throughout the production process such as soil,

winemaker and barrels, that can influence variability in the end product is huge, so shared

practices do not diminish the competitive edge. There is no reason why grape-growers, as

custodians of the land, should not share successes and be brave enough to share failures in

order to drive the industry as a whole towards a sustainable land use approach.

It is incumbent upon the industry to highlight and promote the values of high performing

sustainable producers. Best practice guidelines are more effectively learnt in practice and in

the field rather than the text book, so demonstrations, field walks, and discussion groups or

mentor programs are a great way of sharing knowledge. This is not just applicable to soil

management practices but all aspects of industry, from production to processing and

marketing.

Vineyards take time to develop and mature before the best quality grapes can be produced,

so long-term thinking needs to be employed to maintain the assets. The goal should be to

have healthy, environmentally and financially sustainable vineyards for generations to come.

Openness about failures, as much as successes, is needed to achieve this.

42

Recommendations

“The success of the pioneering farmers draws the sceptics to the waters.” Bob Schindelbeck

Cornell University.

What is required is a considered and consistent long-term approach to sustainable soil

management.

The three P’s need to be utilised in a holistic approach to achieve a vision of long-term

sustainable vineyard health. Traditional European-style farming practices are not suitable to

the older and more fragile soils of Australia and a modern system needs to be utilised

consistently. The keys to this are:

• Minimal topsoil disturbance through tillage.

• Controlled traffic operations and minimal equipment operations during wet periods.

• Occasional ripping to break compaction layers in alternate rows, timed to maximise

root growth into rip lines.

• Remediation and maintenance of soil chemistry and cation balance with gypsum and

lime.

• Perennial vineyard-floor vegetation sown with a diversity of species both midrow and

undervine.

• Utilisation of mulch and compost undervine.

• Promoting the dissemination of practical lessons through discussion groups and

mentor programs.

• Create champions for change, sharing both best practice and recognising failures.

43

References

Buckerfield, J. W. (2001). Managing earthworms in vineyards. Grapegrower and Winemaker,

55-61.

Cass, A. M. (2004). Compost benefits and quality for viticultural soils. American Society for

Enology and Viticulture, 135-143.

Department of Environment. (2010, November 22). Land Theme Report 2001. Retrieved

from Department of Environment:

http://155.187.2.69/soe/2001/publications/theme-reports/land/land04-3.html

Dry, N. (2007). Grapevine Rootstocks: Selection and Management for South Australian

Vineyards. Lythrum Press.

Gillespie, R. a. (2015). Economic Contribution of the Australian Wine Sector. Gillespie

Economics.

Haney, R. (2017, June 12). Siol Scientest USDA- Temple TX. (A. Clarke, Interviewer)

Introductions to soils. (2006, January 1). Retrieved from physicalgeography.net:

http://www.physicalgeography.net/fundamentals/10t.html

Krstic, M. (2017, April 1). (A. Clarke, Interviewer)

Laura Radville, T. B. (2016). Limited linkages of aboveground and belowground phenology: A

study in Grape. American Journal of Botany.

Magdoff, F. V. (2000). Building Soils for Better Crops. Sustainable Agriculture Network.

Mikhail, T. (2010). Is the wrong calcium costing you the earth? Australian and new zealand

grapegrower and winemaker, 40-41.

Ollay, N. (2015, October 5). (A. Clarke, Interviewer)

Rushe, B. (2017, August 6). (A. Clarke, Interviewer)

USDA. (n.d.). soils.usda.gov/sqi/soil_quality/soil_biology/soil_food_web. Retrieved from

USDA Natural Resource Conservation Service.

White, R. E. (2009). Understanding Vineyard Soils. In R. E. White, Understanding Vineyard

Soils.

44

Plain English Compendium Summary

Project Title:

Managing soil structure in established

vineyards

Nuffield Australia Project No.:

1513

Scholar: Andy Clarke

Organisation: Yering Station

Croyden, Victoria 3136

Phone: +61 (0) 417 371 139

Email: aclarke@yering.com

Objectives Investigate and identify novel management methods for the long-term

sustainability of soil structure.

Identify methods of encouraging change practice regarding soil

management in farming operations.

Background The Australian wine industry provides the fifth largest export by value

and is produced in a wide variety of regions, climates and geological

areas. The soils these vines grow in are old and fragile in nature and

are readily degraded when managed utilising traditional European

practice. They are prone to degradation during routine vineyard

operations, reducing productivity and wine quality outcomes in seasons

of extreme weather.

Research Research was mostly undertaken in Spain, France, Germany, Canada,

Ireland and the USA examining vineyard and orchard soil maintenance.

Australian research has also been included as soil conditions and the

challenges they present are quite unique.

Outcomes The current fiscal conditions of the wine industry are not those that

promote large amounts of investment back into the vineyard. Many

gains can, however, be made through better management decisions

with minimal investment. A holistic soil management approach is

required, with an emphasis on soil chemistry, plants and organic

matter. The industry needs to improve how to share failures as well as

our successes.

Implications Vineyards take time to develop and mature before the best quality

grapes can be produced, so long-term thinking needs to be employed

to maintain the assets. The goal should be to have healthy,

environmentally and financially sustainable vineyards for generations

to come. Further research is required on some treatments, though they

look promising.

Publications Presentation of study topic findings at the Nuffield Australia National

Conference, Darwin 2017